Section 3: Weather (11–16%)

Weather dictates drone stability and the distance from which you can safely see hazards.

Atmospheric Stability

Stability is the atmosphere's resistance to vertical motion.

• Stable Air: Resists upward movement. Characterized by stratiform (layered) clouds, steady precipitation, smooth air, and poor visibility (haze/fog).
• Unstable Air: Encourages vertical currents. Characterized by cumuliform (puffy) clouds, showery precipitation, turbulent air, and good visibility.

Thunderstorm Lifecycle

1. Cumulus Stage: Characterized by strong updrafts building the cloud.
2. Mature Stage: Most violent; begins when rain reaches the surface. Features both updrafts and downdrafts.
3. Dissipating Stage: Characterized primarily by downdrafts.

Fog Types

Fog forms when the temperature and dewpoint are within 5°C (~9°F).

• Radiation Fog: Forms on clear, calm nights as the ground cools.
• Advection Fog: Forms when moist air moves horizontally over a colder surface; requires wind.
• Steam Fog: Cold air moves over warm water.

Minimum Requirements

• Visibility: Minimum 3 statute miles (SM) from the control station.
• Cloud Clearance: Minimum 500 feet below clouds and 2,000 feet horizontally from clouds.